32084-13-2Relevant academic research and scientific papers
Scandium triflate-catalyzed intramolecular Friedel-Crafts acylation with Meldrum's acids: insight into the mechanism
Fillion, Eric,Fishlock, Dan
, p. 6682 - 6695 (2009)
The intramolecular Friedel-Crafts acylation of arenes with Meldrum's acid derivatives catalyzed by Sc(OTf)3 was reported as a mild and general entry into functionalized 1-indanones. Mechanistic investigations were undertaken to determine the rate-determining step in the acylation sequence using Meldrum's acid, as well as to examine the role of the Lewis acid catalyst. Enolizable Meldrum's acid derivatives react via an acyl ketene intermediate under thermal conditions, while quaternized Meldrum's acid derivatives are thermally stable and only act as effective Friedel-Crafts acylating agents in the presence of a Lewis acid catalyst. The acylation was postulated to proceed through direct acylation of a Lewis acid-activated carbonyl. In the catalytic Friedel-Crafts acylation of Meldrum's acids, triflic acid appeared to be the active catalytic species, with Sc(OTf)3 serving as a very mild and convenient reagent for its delivery.
An efficient method for generation of α-oxoketenes: Cycloreversion of enolized Meldrum's acid derivatives
Sato, Masayuki,Ban, Hitoshi,Kaneko, Chikara
, p. 6689 - 6692 (2007/10/03)
A series of 6-methoxy- or siloxy-4H-1,3-dioxin-4-ones was synthesized from Meldrum's acids. These dioxinones underwent 4+2 cycloreversion to methoxy- or siloxycartbonylketenes and ketones quantitatively at 20-50°C. The ketenes were characterized by IR spectroscopy as well as by trapping with t-butanol. The ready cycloreversion of these enolized Meldrum's acid derivatives strongly indicates that the anomalously high susceptibility of Meldrum's acids to nucleophilic reagents is due to the participation of carboxyketenes generated through the cycloreversion of tautomeric 6-hydroxydioxinones.
